Optical characterization of single-walled carbon nanotubes synthesized by catalytic decomposition of alcohol

Single-walled carbon nanotubes (SWNTs), synthesized by a catalytic decomposition of alcohol (alcohol CVD method, ACCVD), are compared with high-pressure CO (HiPco) SWNT samples through optical spectroscopic measurements such as resonant Raman scattering, optical absorption and near infrared fluorescence. By the ACCVD method, SWNTs were synthesized either on zeolite catalyst-support particles or directly on the surface of a quartz substrate; in the latter case, a simple dip-coat technique was employed for mounting the metal catalyst. Specific morphological characteristics of as-grown SWNTs generated on zeolite support are presented using SEM and TEM, revealing that the SWNTs produced by the proposed method possess the significant quality of being almost free from amorphous carbons or metal particle impurities. The quality and diameter distribution of SWNTs were investigated and discussed through the results of Raman scattering and optical absorption. The average diameter was slightly smaller for SWNTs grown on zeolite particles than for HiPco SWNTs. Finally, fluorescent emission spectra from isolated SWNTs in an aqueous surfactant suspension were measured for various excitation wavelengths to determine the structural (n,m) distribution of the SWNTs. The narrower chirality distribution for ACCVD SWNTs grown on zeolite compared with HiPco SWNTs was demonstrated.